45
Problem solving
Textbook: Part 2, lesson 45, pp. 19–21
GoalSolve mixed word problems step by step.
New words
problem statement · masala shartiplan · rejaoperation · amalchecking · tekshirish
Explanation
To solve a problem we first read the statement, decide what we need to find and make a plan. Then we do the operations and write the answer with its unit. At the end we check that the answer makes sense. For example, 240 buns packed 8 per box need 240 : 8 = 30 boxes; if a box costs 12 000 sum, that is 30 × 12 000 = 360 000 sum.
Worked examples
A rectangle has perimeter 36 m and length 11 m: its width is 36 : 2 − 11 = 7 m.
A 200-page book: 18 pages a day for 7 days is 126 pages; 200 − 126 = 74 pages remain.
Class activity
“Make a plan”: before solving, write 2–3 questions in your notebook (“what do we find first?”) and then solve.
Practice
1
240 buns are packed 8 per box. If each box costs 12 000 sum, how many sum do all the boxes cost?
360000
2
A rectangle has perimeter 36 m and length 11 m. How many m is its width?
7
3
A book has 200 pages. Zarina read 18 pages a day for 7 days. How many pages are left?
74
4
On a ray A(7) and B(19), e = 3 m. How many m is AB?
36